Kurdish officials and a Britain-based monitor said the two IS suicide attacks targeting the border post were launched from Turkish soil, claims that Turkish officials dismissed as "lies".
The attacks sparked fierce clashes between IS and Kurdish People's Protection Units (YPG) forces that have been fighting for more than two months to protect the border town of Kobane from jihadist capture.
"Clashes broke out for the first time in the area after two jihadist attacks at dawn on the border post separating Turkey and Kobane," said Rami Abdel Rahman, head of the Syrian Observatory for Human Rights monitoring group.
One suicide attacker blew up an explosive-packed car and another detonated a suicide-bomb belt, according to the Britain-based Observatory.
IS began its assault on Kobane, the third largest Kurdish town in Syria, more than two months ago, but Kurdish fighters backed by US-led air strikes and Iraqi Kurdish peshmerga forces have so far prevented a full takeover of the town.
The Observatory said 28 people - 20 IS jihadists and eight YPG fighters - had been killed in clashes in Kobane over the past 24 hours, including the two suicide bombers.
There were conflicting claims about how Saturday's bombings were launched, with the Observatory saying the attackers "came from Turkish territory".
Kurdish officials and activists repeated that claim, but it was strenuously denied by Turkish officials and the military.
"Claims that the car involved in the IS attack on the Mursitpinar border post came from Turkey are lies," the army said in a statement quoted by Turkish media.
